The present invention relates to 3D printing and to a method and apparatus for the forming of 3D structures onto surfaces.
The present invention addresses the problem of accurate and fast formation of 3D features onto a surface. This problem is a concern in a wide range of areas, a number of which are described below.
In one example, people who use Braille for communication are particularly affected by a shortage of accurate and fast means for producing the Braille characters. One known method is to use impact printers to emboss paper with raised portions representing the Braille characters. Compared with conventional printers, however, the impact printers can be expensive due to their complexity, noisy due to the constant impacting of the printer head and unreliable due to the high forces on the moving parts.
Drop-on-demand printing is a known printing technique whereby a droplet of ink is ejected from a inkjet printer head. The droplet impacts with a printing surface, dries and forms a spot which forms a recognizable pattern such as type. This technique has proved to be an efficient and economical way of printing using ink and its use is now widespread.
According to one aspect of the present invention there is provided a method of forming a three dimensional feature on a surface using the technique of drop ejection to deposit droplets of deposition material, said method comprising depositing a plurality of droplets on said surface to form a feature comprising multiple discrete portions, at least two adjoining portions being formed from different deposition material.
Preferably the plurality of droplets comprise at least one droplet of one material and at least one droplet of another material.
The application of the invention is wide. For instance, tactile character sets for the sightless such as Braille, Dotsplus, ASTeR, Moon print and such like may be formed as easily as conventional character sets. Accordingly, in a second aspect, the present invention provides a method of forming a Braille character on a surface using the technique of drop ejection to deposit droplets of deposition material, said method comprising depositing a plurality of droplets on said surface to form a character comprising multiple discrete portions, at least two adjoining portions being formed from different deposition material.
Conventional printing tasks may be performed using the present invention including, for example, warning symbols, product advertising, xe2x80x98Thermographicxe2x80x99 printing or wall paper printing. Tactile digital photography is possible for the production, say, of relief maps. The photograph is constructed from digital data including the height of the ground stored as discrete steps which defines the size or number of drops of print material applied. Upon ejecting or curing of the deposition material the individual drops combine with neighbouring drops so that the height varies continuously and not in discrete steps. Different deposition materials may be dropped onto the surface to give different textures.
Another application is textile patterning where, for instance, names or emblems can be printed directly on to teeshirts or sweatshirts. Alternatively a roll of fabric or carpet can be printed with a recurring pattern.
Another application is in coating of whole areas whereby the thickness of a laminate may be controlled. Particular use may be found in PCB production, adhesives, transparent electrodes (e.g. using co-polyaniline based solutions), optical elements (e.g. the anti-reflective coating of ophthalmic lenses) and protection of display windows. Alternatively the coating may be on a selected area only. For instance the direct writing of masks on PCBs, selective adhesives and discrete transparent electrodes.
The nozzles may be adapted to spray the deposition material, the deposition area being dictated by the number of nozzles that are fired. High precision coatings are possible using this method of ejecting a blanket area of material.
An important application of the invention is in the formation of surface structures such as waveguides for microwaves and light. In the latter case a ferroelectric optic waveguide may be built with drops of a ferroelectric material which may be thermally annealed to crystallise and set the ferroelectric properties. In a third aspect, the present invention provides a method of forming a multi-layer optical device on a surface using the technique of drop ejection to deposit droplets of deposition material, said method comprising depositing a plurality of droplets on said surface to form a device comprising multiple discrete portions.
Thin film techniques such as amorphous silicon deposition, LCD display fabrication, gas sensor fabrication and microlens formation are all possible applications of the invention. Formation of non-linear optical devices and polymer transistor structures are also possible applications.
Preferably, the deposition materials comprise between 20% and 60% solid material. Advantageously the deposition material comprises between 30% and 50% solid material and more advantageously the deposition material comprises substantially 40% solid material.
Using such a method a specific feature can be deposited with a selectable profile which is not solely determined by the deposited material (e.g. rheology, surface wetting, thixotropy). The method allows application of a multiplicity of drops, co-incident upon one point in order to build up the required feature.
Preferably the deposition material has a dynamic viscosity in the range 1 cps and 1000 cps and more preferably between 1 cps and 200 cps.
Advantageously the method further comprises the step of subjecting the deposition material to radiation treatment before, during or after deposition. The print surface may be subjected to radiation to prepare it for the deposition material. Employing in-situ UV and infrared radiation exposure provides considerable scope for modifying the reaction of the drop in order to achieve the required feature and profile.
Preferably the radiation is ultraviolet light. In this case the deposition material suitably comprises oligomers such as epoxy acrylics or urethane acrylics and more suitably said epoxy acrylics are silicone loaded. The silicon loading decreases the surface energy of the print material and renders the print material non-stick. Alternatively the deposition material suitably comprises urethane acrylics.
Preferably the radiation is infrared light. In this case the deposition materials suitably comprises water miscible partially reacted polymers.
Preferably, one of said layers comprises a printing surface treatment layer, preferably comprising epoxy acrylic.
Advantageously the method further comprises the step of raising the temperature of the deposition material prior to deposition. This decreases the dynamic viscosity of a deposition material so that it may be used in the drop-on-demand method. Such a material is a hot melt material.
Advantageously the method further comprises utilising one or coincident droplets of a cross-linkable polymeric materials and initiating the cross-linking in-flight or immediately after deposition. The initiating of the cross-linking may be by chemical means using a further coincident drop or by the radiation treatment.
In a fourth aspect, the present invention provides droplet deposition apparatus having multiple droplet deposition nozzles for the deposition of different deposition materials on a printing surface to form a three dimensional feature comprising multiple discrete portions, adjoining portions being formed from different deposition material.
The nozzles may be directed towards at a single droplet deposition site. Preferably, the nozzles deposit different deposition materials to form a feature comprising three or more portions, said portions comprising a sealant portion, a body portion and a portion formed from non-stick material.
Preferably, the droplet deposition apparatus further comprises electromagnetic means for establishing an electromagnetic field for treatment of material ejected from the nozzles. The electromagnetic means may comprise at least one waveguide or optical fibre communicating with a continuous or pulsed ultraviolet, visible light or infrared source.
The electromagnetic means may be operable at at least two discrete wavelengths.
The electromagnetic means may further comprise a focus arrangement for directing the electromagnetic radiation. Alternatively, the electromagnetic means may further comprise a scanning arrangement such as a rotating mirror.
Preferably, the apparatus comprises a deposition chamber and a shutter actuable to shield material within the chamber from an electromagnetic field.
Preferably, the apparatus further comprises a deposition chamber and actuator means in or adjacent the deposition chamber for the application of a pressure pulse to the deposition chamber, wherein the actuator means comprises a bimorph laminate including at least two layers of piezoelectric material and at least two metal layers. The actuator means may comprise at least three actuators arranged so as together to define the wall of at least part of the chamber.
Alternatively, the apparatus may further comprise a deposition chamber and actuator means in or adjacent the deposition chamber for the application of a pressure pulse to the deposition chamber, wherein the actuator means comprises at least three actuators arranged so as together to define the wall of at least part of the chamber.
The actuator means may comprise four actuators providing a rectangular cross-section for said part of the chamber.
The apparatus may further comprise means for the simultaneous firing of the actuators.
Preferably, the apparatus further comprises a nozzle shutter associated with each respective nozzle for closing that nozzle. The nozzle shutter may comprise a plunger housed in the deposition chamber and moveable between a closed position in which the head of the plunger aligns with the aperture of the nozzle and an open position in which the plunger is retracted into the deposition chamber. Preferably, the nozzle shutter comprises a bimorph laminate including at least two layers of piezoelectric material.
The apparatus may further comprise means for varying the size of the aperture of at least one of said nozzles. The means may comprise an iris-type diaphragm associated with the or each nozzle.
In a fifth aspect, the present invention provides a method of printing employing drop on demand ink jet apparatus comprising a droplet deposition head comprising a deposition chamber, actuator means associated in or adjacent the chamber for the application of pressure, a second, down-stream chamber and corresponding actuator means, said method comprising the steps of:
actuating the actuator means associated with or adjacent to said down-stream chamber to create a pressure pulse in droplet deposition material contained in the deposition chamber; and
actuating the actuator means associated with or adjacent to said deposition chamber to create a pressure pulse in droplet deposition material contained in the deposition chamber to cause droplet ejection from the deposition chamber.
Preferably, the pressure pulses create standing waves of different frequency in droplet deposition material contained in the droplet deposition head.
In a sixth aspect, the present invention provides droplet deposition apparatus comprising a deposition chamber, actuator means associated in or adjacent the chamber for the application of pressure, wherein there is provided a second, down-stream chamber and corresponding actuator means whereby pressure pulses are appliable independently to the down-stream chamber.
Preferably the pressure pulses are appliable synchronously to the deposition chamber by both said actuator means.
The actuators may be adapted to create standing waves of different frequency in droplet deposition material contained in the droplet deposition head.